Salmonella has become unfortunately recognized as a serious health concern in food products intended for human consumption. Salmonella is of particular concern in meat products because of its potential presence in livestock, particularly cattle, swine and poultry, at various stages in their growth cycle. Although the risk of salmonella-caused illness in humans can be greatly reduced--and indeed eliminated--by proper handling techniques during food preparation and storage (both commercial and domestic), eliminating salmonella at the earliest possible point in the food production chain remains a desirable goal.
To this effect, significant progress has been made in recent years in fighting salmonella using probiotic techniques and compositions rather than antibiotics or other pharmaceutical compositions. As used herein, the term "probiotic" refers to compositions or organisms that do not attack the salmonella bacteria as would a pharmaceutical composition, but rather that replace the salmonella in the host animal with a more beneficial bacteria, or with a bacteria that simply prevents the salmonella bacteria from gaining a useful foothold from which it can continue to contaminate, or indeed increase its contamination of, the host animal and the animals to which the host spreads the salmonella. Such compositions are also referred to as "competitive exclusion" products.
Exemplary probiotics for use with poultry are set forth in U.S. Pat. Nos. 5,308,615; 5,340,577; and 5,478,557, the contents of which are incorporated entirely herein by reference.
In order to work successfully, however, the probiotic must be taken up by the target animal, in this case poultry. For example, the probiotics set forth in the '615, '577, and '557 patents must be ingested by poultry in a manner that places the probiotic composition in the digestive tract. Conventionally, this can be done using oral gavage, or by mixing the probiotic with feedstuffs or drinking water that the poultry are expected to ingest. Furthermore, the nature of probiotics is such that they are most effective--and in some cases solely effective--when ingested shortly after an animal's birth. Stated differently, because in most cases the probiotic is a preventative measure, it must be in place in the animal's digestive tract before salmonella can gain a foothold.
Each technique presents certain problems. Oral gavage is the most effective technique: every bird gets the correct dose. Nevertheless, oral gavage requires that each individual bird be handled and fed the probiotic. To date such handling is almost exclusively dependent upon manual labor, thus increasing the cost, particularly given the large number of poultry processed for human consumption on a regular basis. Using feedstuffs can lack precision because the dosage received by any one bird depends both upon the proportion in which the probiotic is mixed with the feed as well as the amount of food that any particular bird eats.
Mixing the probiotic with the drinking water introduces potentially troublesome factors such as water purity and expected differences in water from place to place (i.e. the particular minerals and other items present). Additionally, dilution must be carefully controlled. Perhaps most importantly, certain presently preferred probiotics (including those referred to herein) have a relatively short effective lifetime (sometimes as short as a few minutes) and thus must be ingested rather quickly once presented to the birds. As a result, if the birds fail to drink enough water during the probiotic's effective lifetime, the treatment will have little or no effect.
Furthermore, the difficulties inherent in gavage, feed mixing, or drinking water are exacerbated in very young birds.
Most previous experimentation with spray-applied biologies has involved the use of viral vaccines, such as infectious bronchitis and Newcastle vaccines. As the primary portal of entry for these biologies involves occular or respiratory routes, little research has addressed the conditions necessary for optimal ingestion of spray-applied products. As competitive exclusion cultures apparently must be ingested for optimal colonization of the intestinal tract, modifications of photointensity regimes that favor actual preening activity, and preening as so elated ingestion of spray-applied products, may be important for optimal performance of these cultures.
Competitive exclusion, consisting of undefined adult chicken intestinal microflora, was first described and implemented by Nurmi and coworkers when Salmonella infantis outbreak occurred in Finland; Nurmi, E., and M. Rantala, 1973, New Aspects of Salmonella Infections in Broiler Production, Nature 241:210-211. Since then, a variety of delivery systems have been compared and spray application has been demonstrated to be equally protective as drinking water application by several laboratories; Corrier, D. E. et al., 1994, Competitive Exclusion of Salmonella Enteritidis in Leghorn Chicks; Comparison of Treatment by Crop Gavage, Drinking Water, Spray, or Lyophilized Alginate Beads, Avian Dis. 38:297-303; Schneitz, C., 1992, Research Note: Automated Droplet Application of a Competitive Exclusion Preparation, Poultry Sci. 71:2125-2128; Blankenship, L. C. et al., 1993, Two-step Mucosal Competitive Exclusion Flora Treatment to Diminish Salmonellae in Commercial Broiler Chickens, Poultry Sci. 72:1667-1672. Since that time, effective and defined competitive exclusion products have been developed and are commercially available in the United States; Corrier, D. E., et al., 1993, Development of Defined Cultures of Indigenous Cecal Bacterial to Control Salmonellosis in Broiler Chicks, Poultry Sc. 72:1164-1168; Corrier, D. E. et al., 1998, Dosage Titration of a Characterized Competitive Exclusion Culture to Inhibit Salmonella Colonization in Broiler Chickens During Growout; J. of Food Protection 61:796-801; Hume, M. E. et al., 1998, Reduction of Caecal Literia Monocytogenes in Leghorn Chicks Following Treatment with a Competitive Exclusion Culture (PREEMPT.TM.), Letters in Applied Microbiology 26:432-436; Hume, M. E. et al., 1998, Early Salmonella Challenge Time and Reduction in Chick Cecal Colonization Following Treatment with a Characterized Competitive Exclusion Culture, J. of Food Protection 61:673-676. Application to large numbers of chicks under commercial conditions must be efficient, should be administered as early in life as possible; Schneitz, C. et al., 1992, Competitive Exclusion in the Young Bird: Challenge Models, Administration and Reciprocal Protection, International J. of Food Microbiology, 15:241-244, and should minimize uncontrolled variables such as water quality and proportioner/medicator function and consistency. Automated spray application therefore offers several advantages over drinking water or individual administration by gavage. However, much of the spray-applied product is not ingested by the chick, reducing the percentage of the applied dose that is actually ingested.
Because commercially available defined cultures are relatively expensive to produce under controlled conditions (e.g. PREEMPT.TM., improved delivery, through enhanced preening activity and preening-associated ingestion of spray-applied product, is an important aspect of commercial use of such products.
Accordingly, a need exists for a method of making sure that very young birds--i.e., chicks--can and will be dosed with sufficient amounts of a desired probiotic to insure that the probiotic has the desired effect against salmonella infection.